Fix based on review

Author: KodaiD

core/src/main/java/com/scalar/db/storage/objectstorage/ClusteringKeyComparator.java

@@ -4,6 +4,7 @@
 import com.scalar.db.api.Scan;
 import com.scalar.db.api.TableMetadata;
 import com.scalar.db.io.Column;
+import com.scalar.db.io.DataType;
 import java.util.Comparator;
 import java.util.Map;
 
@@ -19,12 +20,11 @@ public int compare(Map<String, Object> clusteringKey1, Map<String, Object> clust
     for (String columnName : metadata.getClusteringKeyNames()) {
       Scan.Ordering.Order order = metadata.getClusteringOrder(columnName);
 
+      DataType dataType = metadata.getColumnDataType(columnName);
       Column<?> column1 =
-          ColumnValueMapper.convert(
-              clusteringKey1.get(columnName), columnName, metadata.getColumnDataType(columnName));
+          ColumnValueMapper.convert(clusteringKey1.get(columnName), columnName, dataType);
       Column<?> column2 =
-          ColumnValueMapper.convert(
-              clusteringKey2.get(columnName), columnName, metadata.getColumnDataType(columnName));
+          ColumnValueMapper.convert(clusteringKey2.get(columnName), columnName, dataType);
 
       int cmp =
           order == Scan.Ordering.Order.ASC

core/src/main/java/com/scalar/db/storage/objectstorage/SelectStatementHandler.java

@@ -205,12 +205,12 @@ private boolean isReverseOrder(Scan scan, TableMetadata metadata) {
         throw new IllegalArgumentException(
             CoreError.OPERATION_CHECK_ERROR_ORDERING_NOT_PROPERLY_SPECIFIED.buildMessage(scan));
       }
-      boolean rightOrder =
+      boolean isValidOrder =
           ordering.getOrder() != metadata.getClusteringOrder(ordering.getColumnName());
       if (reverse == null) {
-        reverse = rightOrder;
+        reverse = isValidOrder;
       } else {
-        if (reverse != rightOrder) {
+        if (reverse != isValidOrder) {
           throw new IllegalArgumentException(
               CoreError.OPERATION_CHECK_ERROR_ORDERING_NOT_PROPERLY_SPECIFIED.buildMessage(scan));
         }

core/src/main/java/com/scalar/db/storage/objectstorage/StatementHandler.java

@@ -128,7 +128,7 @@ protected void validateConditions(
         throw new ExecutionException(
             String.format(
                 "A condition failed. ConditionalExpression: %s, Column: %s",
-                expectedColumn, actualColumn));
+                expression, actualColumn));
       }
     }
   }